Understanding the biomechanical properties of body tissues, particularly internal tissues or organs, is useful for the development of improved medical diagnostic and treatment tools. In addition, understanding the biomechanical properties such as the elastic and visco-elastic properties of internal tissues or organs can aid in designing more safe, comfortable and effective devices for internal use. Biomechanical implications learned from these measurements can improve not only the design of medical devices and implants used for minimally invasive surgery, but also any other products interacting with body tissues. As an example, knowledge of biomechanical properties can help in developing a better understanding of the effects of internally worn devices such as tampons on the deformations in internal tissues to the point of affecting comfort and effectiveness.
External tissues and organs such as the stratum corneum and epidermis can be relatively easily characterized for in vivo mechanical properties because of easy accessibility and locating the point of measurement. However, internal tissues and organs, such as intra-abdominal tissues, intra-vaginal tissues, intra-uterine tissues, intra-esophageal tissues, and the likes are more difficult to characterize. In particular, in-vivo measurements of internal tissues to obtain biomechanical properties are difficult due to limited accessibility nature of such tissues and difficulties associated with locating the point of measurement. The constraints of available devices and techniques to reach these tissues, as well as the difficulty of obtaining accurate data under in vivo condition has hampered efforts at accurately modeling of ‘living’ internal tissue biomechanical properties.
In-vivo measurements of internal tissues properties of organs such as the vagina are particularly difficult to achieve. The human female vagina is located in the lower pelvic cavity and surrounded by the major organs such as the uterus, the bladder, and the rectum. The vagina is a collapsed tube-like structure composed of fibromuscular tissue layers. The central portion has an H-shaped cross section and its walls are suspended and attached to the paravaginal connective tissues. The vaginal inner walls have rugal folding which is extended significantly during delivery. Smooth muscle fibers are oriented along the vaginal axis and arranged circularly toward the periphery. Vaginal walls are connected to the lateral pelvic floor by connective tissues and smooth muscle layers, which allow the vagina to be deformed and displaced easily according to the external strain energy applied.
The pelvic environment comprises a soft tissue and muscle “hammock” to which the various organs are attached. For example, the vagina is connected to the pelvis by the pelvic floor muscles and connective tissue. Because of its location within pelvic cavity, the degree of vaginal tissue deformation is significantly influenced by the biomechanical properties of surrounding organs and tissues. Furthermore, because there is no rigid supporting structure around the vagina, but connective tissues of smooth muscle fibers among the surrounding organs, it is important to understand not only deformation of vaginal tissues, but also surrounding organs' boundaries for complete measurement of biomechanical properties and parameters of vaginal and surrounding tissues. Among the surrounding organs of vagina, the bladder is the most influential organ in a way that the vaginal tissue responds to external strain; as the bladder expands by accumulating urine, it stretches toward vesicovaginal tissue layers. The apparent physical change is deformation (stretching and/or compaction) of tissue layers, which can in turn impact the stiffness of tissue layers. Interactions among the lower pelvic floor organs make the in vivo measurement of vaginal tissue more challenging work. Therefore, these anatomical complexities of the vagina and surrounding tissues and organs require that biomechanical properties be obtained by considering the heterogeneous and inhomogeneous nature of the related human anatomy, and interactions of neighboring organs and tissues.
Accordingly, there is a continuing unaddressed need for better devices and methods for determining biomechanical properties of internal tissues and organs. The new measurement method is preferably non-invasive or at least minimally invasive, so the mechanical properties of the original tissues are well maintained while the measurement is underway.
Further, there is a continuing unaddressed clinical need for devices and methods for measuring biomechanical tissue properties in-vivo, such that the effects of surrounding tissues and organs are taken into account.
Additionally, there is a continuing unaddressed need for a device and method for determining the biomechanical properties of different portions of the same tissue or organ.